I would think that a short distance sprint bike would be best as the rider is putting max effort over a short amount of time. If you are doing an experiment and using the quoted 2 minutes I would think that what I mentioned would do you. Now the question is what type of bike is used for short sprints?

I'll make the assumption that the sprint bikes are similar in nature and that the gearing system is slightly different to account for the differences in riders.

Cool machine, but it doesn't look like the rider is taxing the 'energy delivery' capabilities of the bike at all. Rider technique and fitness look quite low; for a two minute effort, I'd expect a more linear buildup and hard sprint at the end. Any idea how much power it takes to get the flywheel up to speed? Higher cadence pedaling would be attractive here, I think.

That said, the bike needs to be much more solidly mounted, like forks clamped in a stand, and I'd probably go drop bars so the rider can pull better.

Mentioned above we already know current bike frame is too small. Seat tube is usually fully extended, but has been overlooked occasionally.

For a 2min sprint on static rollers weight , aerodynamics and comfort are not needed.
You need a crank the correct length for the rider. This is the starting point for saddle and bar positioning. You can experiment with saddle fore-aft and height. Bar reach and height should be correct to maximise upper body contribution. "Look" made a solid adjustable stem.
A frame and transmission stiff enough to have zero flex.
The transmission and rear wheel weight may have an impact but if the roller resistance is the deciding factor, then not.
On singlespeed systems, you want larger rings and sprockets for better transmission efficiency.
If you have big rings you need thick metal to avoid flex which may mean a 1/8" track style chain.
A solid pedal to shoe connection with a very stiff midsole. Track riders are more concerned with sold connection than with a safe release mechanism so straps are still in use.

This was my first week on the machine. The bike is too small, cheap and not sized correctly so my technique is agreeably not what it should be. My cadnence was also not ideal. This is not like riding an ordinary bike, so it takes some getting used to. There's a HUGE dead zone at the top and bottom of the stroke especially at the low range. I am a solid B/B+ rider and competitive triathlete. Surprised you can diagnose my fitness level from that clip.

The shot in the clip was a ramp up to a target RPM, not a timed shot. Don't know the answer how much power it takes to spin up. We're curious about that and are hoping to add a power meter to the system (bottom bracket? Garmin Vector pedals?). Currently only using a cycling computer w a magnet on the main wheel to read rpms.

Last year the builder left the front suspension on the MTB. We convinced him to lock it out for this year. Will engineer some type of a fix for the front end.

Great idea!

I'll take some pictures of the drivetrain this weekend and post so you all have a better idea of how this thing is built.

BTW - We shot at the World Championships of Punkin Chunkin last weekend and won with a shot 1776' (a world record for a human powered centrifugal machine). Looking to glean as much as I can from everybody here and improve for next year. So thank you all for your input!

Yes, I'm sorry...I should not have spoken like I could ascertain fitness from that brief clip, and your explanation of the dead zone shows why; I don't know how the transmission works, and all I could see was the uneven cadence. I'm sorry to have offended you.

I think looking at the transmission, then, should take precedence over all else, since you're losing a huge amount of power in those dead zones. Next, I'd focus on cadence and power, and then start looking at the bike. I really believe that for 2mins of riding, the bike won't make any difference, provided you're getting the leg extension you need and have room jump out of the saddle for the last 10-20 seconds during the sprint.

I am, clearly, assuming that maximizing flywheel velocity is the goal; is that correct?

Holy cow! That's more than a quarter of a mile! Congrats!

@chaadster Not a problem.

Quote:

Originally Posted by chaadster

maximizing flywheel velocity is the goal; is that correct?

You are correct. Max out the RPM's.

We have not passed 300 RPM with current setup but believe its easily obtainable. Still addressing efficiency (trying to remain topical), suggestions for a new drivetrain? What options should we look at? I will admit that I'm weak on the math here. Suggestions for a rear cassette set-up? Should we consider a big 55+T ring up front? Triple crankset?

I suppose I'd need to see some pics of it before I could even start making reccos there, but I'm out of my depth when it comes to engineering, anyway, so I probably wouldn't be of help anyway.

I how many gears are you using for a competition wind-up now?